Rockwell Automation 1756-HIST2G Historian ME 2.1 - Manual (Page 309)

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G LOSSARY
Slot Number The number that indicates the physical location of the slot in
the chassis where the module or controller resides.
Snapshot Event Either any event sent to the Snapshot subsystem or the event
currently residing in the Snapshot table for a particular point.
The event stored in the Snapshot table for each point has the
most recent timestamp of all events received so far for that
point; when a new event arrives with a more recent timestamp,
the previous event is passed through the compression filter.
Snapshot Subsystem The core component of the FactoryTalk Historian ME server
that receives all the new data events for all points regardless of
the sending application. The most recent of these events for
each point is maintained in the Snapshot table along with
additional information necessary to perform compression.
Span The base point attribute that specifies the range or the
difference between the maximum and minimum values for a
point.
SQC See Statistical Quality Control.
Statistical Quality
Control (SQC)
The SDK-based Add-In to FactoryTalk ProcessBook that
enables users to create and view a variety of SQC charts on
their FactoryTalk ProcessBook displays.
String Point Type The point type used for storing strings, sequences of
alphanumeric characters, up to 976 characters in length.
Swinging Door
Compression
A data compression algorithm used by the Snapshot subsystem
that guarantees all of the original samples were within a
specified value, the compression deviation, of a straight line
drawn between any two events selected for archiving. In other
words, this compression algorithm allows for the
reconstruction of the original signal as a series of straight lines,
and the maximum error between the reconstructed and original
signals is guaranteed to be no more than the compression
deviation.
Tag The base attribute that is the unique alphanumeric name for a
point. Certain characters are not allowed like ‘*’, ‘?’, ‘\’, and
‘;’. The terms Tag and Point are often used interchangeably.
Term Definition